Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
  • C08C19/00—Chemical modification of rubber
  • C08C19/30—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule
  • C08C19/42—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule reacting with metals or metal-containing groups
  • C08C19/44—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule reacting with metals or metal-containing groups of polymers containing metal atoms exclusively at one or both ends of the skeleton
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
  • B60C1/0016—Compositions of the tread
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08L9/06—Copolymers with styrene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/16—Elastomeric ethene-propene or ethene-propene-diene copolymers, e.g. EPR and EPDM rubbers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/18—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms
  • C08L23/20—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms having four to nine carbon atoms
  • C08L23/22—Copolymers of isobutene; Butyl rubber ; Homo- or copolymers of other iso-olefins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/26—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers modified by chemical after-treatment
  • C08L23/28—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers modified by chemical after-treatment by reaction with halogens or compounds containing halogen
  • C08L23/283—Halogenated homo- or copolymers of iso-olefins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L7/00—Compositions of natural rubber
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08L9/02—Copolymers with acrylonitrile
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08L9/06—Copolymers with styrene
  • C08L9/08—Latex
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
  • Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction 

Definitions

• This invention relates to a rubber composition for a tire tread, and more particularly to a rubber composition suitable for use in a tread of a pneumatic tire considerably reducing rolling resistance without degrading wet-skid resistance, fracture resistance and wear resistance.
• the rolling resistance and wet skid resistance of the tire are theoretically related to viscoelastic properties of the rubber composition.
• it is effective to decrease the hysteresis loss of the tread rubber for reducing the rolling resistance during the running of the tire, or viscoelastically decrease the loss tangent (tan ⁇ ) at a temperature of 50-70° C. corresponding to the running tire temperature in order to obtain a low fuel consumption.
• the wet skid resistance is well interrelated to the loss tangent at about 0° C. under a frequency of 10-20 Hz, so that it is necessary to increase the loss tangent at about 0° C. in order to improve the gripping property of the tire.
• a rubber material having a low glass transition temperature (Tg) such as high-cis polybutadiene rubber or a rubber material having a high rebound resilience such as natural rubber.
• an object of the invention to solve the above problems and to provide a rubber composition suitable for use in a tread of a pneumatic tire considerably reducing rolling resistance without degrading wet-skid resistance, fracture resistance and wear resistance.
• the styrene-isoprene copolymer before the coupling treatment contains a butadiene bond at its terminal.
• the styrene-isoprene copolymer according to the invention is an anion-polymerized styrene-isoprene copolymer having a bound styrene content of 5-25% and a content of 1,2- and 3,4-bonds in bound isoprene portion of 5-35%.
• bound styrene content is less than 5%, the strength at fracture is poor and tan ⁇ (0° C.) is low to degrade the wet skid resistance, while when it exceeds 25%, the hysteresis loss is large and the rolling resistance is poor.
• this copolymer is required to be used in an amount of 30-100% by weight as a rubber ingredient.
• the amount of the copolymer used is less than 30% by weight, the low rolling resistance and the wet-skid resistance can not simultaneously be established.
• the styrene-isoprene copolymer according to the invention is produced by anion polymerization of isoprene monomer and styrene monomer.
• lithium type initiators which include, for example, methyllithium, ethyllithium, propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, hexyllithium, octyllithium, phenyllithium, cyclohexyllithium, 1,4-dilithiobutane and the like.
• n-butyllithium and sec-butyllithium are preferable.
• lithium type initiators may be used alone or in admixture. Moreover, the amount of the lithium initiator used is within a range of 0.2-20 mmol per 100 g of the monomer.
• the polymerization is carried out at a temperature of -20° C. to 150° C., preferably 20-120° C.
• the polymerization reaction may be conducted under temperature rising or under isothermal condition.
• hydrocarbon solvent used in the anion polymerization according to the invention there are aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons. Among them, it is favorable to use one or two hydrocarbons selected from the group consisting of propane, n-butane, i-butane, n-pentane, i-pentane, cis-2-butene, trans-2-butene, i-butene, 1-butene, n-hexane, n-heptane, n-octane, i-octane, methylcyclopentane, cyclopentane, cyclohexane, 1-hexene, 2-hexene, 1-pentene, 2-pentene, benzene, toluene, xylene, ethylbenzene and so on.
• the concentration of the monomer in the solvent is within a range of 5-50% by weight, preferably 10-35% by weight.
• the ratio of the modified copolymer bonded at its terminal with the tin compound is not less than 30% by weight per total copolymer.
• the ratio of the modified copolymer is less than 30% by weight, the heat build-up becomes high.
• the ratio of the modified copolymer is not less than 50% by weight for obtaining low heat build-up.
• X is a halogen atom, preferably chlorine or bromine.
• R is an alkyl group
• the carbon number is preferably 1-20
• R is an alkenyl group
• the carbon number is preferably 2-20 because it is difficult to obtain tin compounds in which the carbon number of R exceeds 20.
• R is a cycloalkyl group or an aryl group
• the carbon number is preferably 6-20.
• tin compound mention may be made of tin tetrachloride, tin tetrabromide, butyltin trichloride, methyltin trichloride, octyltin trichloride, dimethyltin dibromide, dimethyltin dichloride, dibutyltin dichloride, diphenyltin dichloride, 1,2-bis(trichlorostannyl) ethane, 1,2-bis(methyldichlorostannyl) ethane, 1,4-bis(trichlorostannyl) butane, 1,4-bis(methyldichlorostannyl) butane, ethyltin trisstearate, butyltin trisoctanoate, butyltin trisstearate, butyltin trislaurate, dibutyltin bisoctanoate, dibutyltin bisstearate, dinutyltin bisl
• dimethyltin dichloride dimethyltin dibromide, dibutyltin dichloride, diphenyltin dichloride, butyltin trichloride, methyltin trichloride, tin tetrachloride, tin tetrabromide and the like are preferable.
• the bifunctional tin compounds are most preferable.
• the amount of the tin compound used is within a range of 0.4-1.5 equivalent as a halogen atom per 1 equivalent of anion in the polymer.
• the coupling reaction between the tin compound and the active terminal of the copolymer is usually carried out at a temperature of 30-120° C. for 0.5-1 hour.
• the coupling reaction with the halogenated tin compound is carried out after a given amount of butadiene is added to anion of styrene-isoprene copolymer.
• Carbon black used in the rubber composition according to the invention is not particularly critical in the kind and the amount.
• the amount of carbon black used is preferable to be 20-150 parts by weight.
• carbon black used in the invention mention may be made of (i) gas furnace black, (ii) channel black, (iii) carbon black obtained by subjecting the furnace black (inclusive of oil furnace black and gas furnace black) to an oxidation treatment with an oxidizing agent such as HNO 3 , H 2 O 2 , O 3 , dichromate or the like, (iv) carbon black obtained by subjecting gas furnace black or channel black to a heat treatment at a temperature of 100-900° C., (v) carbon black obtained by further subjecting the oxidized carbon black of the item (iii) to a heat treatment at a temperature of 100-900° C., (vi) carbon black obtained by treating gas furnace black or channel black through a low-temperature plasma process, and the like.
• carbon blacks of the items (iii) and (v) are preferable from a viewpoint of the reinforcing effect.
• the rubber ingredient other than the above defined styrene-isoprene copolymer mention may be made of natural rubber and synthetic rubbers such as emulsion-polymerized styrene-butadiene copolymer, solution-polymerized styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer (NBR), butyl rubber, ethylene-propylene-diene terpolymer, halogenated butyl rubber and the like.
• natural rubber and synthetic rubbers such as emulsion-polymerized styrene-butadiene copolymer, solution-polymerized styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer (NBR), butyl rubber, ethylene-propylene-diene terpolymer
• the rubber composition according to the invention is used by properly compounding with an antioxidant, zinc white, stearic acid, a vulcanization accelerator, a vulcanizing agent and the like in addition to the aforementioned carbon black.
• the coupling agent is added so that mol number of halogen atom is equal to that of lithium atom.
• the microstructure of the polymer is measured by means of proton NMR.
• the coupling efficiency (CE) indicates a ratio of polymer having tin-carbon bond to total polymer and is measured from an area ratio of high polymer component to low polymer component in a curve measured by a gel permeation chromatography (GPC: HLC-8020 made by Toso Company, column: GMH-XL (two columns in series) made by Toso Company).
• Carbon black a is ASTM code N339.
• Carbon black b is obtained by subjecting ASTM code N330 to an oxidation at room temperature in an ozone atmosphere for 3 hours and then heating at 450° C. in a nitrogen gas atmosphere for 1 hour.
• Carbon black c is a channel black of special black 4A (trade name, made by Dixie) subjected to oxidation treatment.
• each of these flasks is put into an oil bath held at 100° C. and maintained at this temperature for 16 hours.
• 50 ml of 3 normal hydrochloric acid is added to the reaction product while cooling to neutralize an excessive amount of hydroxylamine.
• the reaction product is filtered under suction to obtain dispersion of oximed carbon black, which is washed with about 300 ml of distilled water.
• the oximed carbon black is placed on a filter paper of No. 5B and further washed with 800 ml of the distilled water.
• the oximed carbon black is placed in a dryer held at 105° C. and dried up to a constant weight, whereby the oximed carbon black is prepared. (The same procedure as mentioned above is repeated in the flask for blank test).
• the decomposition bottle is attached to a semi-micro Kjeldahl decomposition device and then gas is ignited while flowing tap water through an exhaust gas suction aspirator.
• the intensity of flame is first weakened to an extent that the content in the bottle is not boiled and then gradually strengthened to an extent that the content is boiled if the occurrence of white smoke becomes small in the bottle.
• the ignition is further continued for 1 hour.
• the bottle is taken out from the device and added dropwise with about 10 ml of the distilled water.
• the content in the bottle is placed into a sample flask of a semi-micro Kjeldahl nitrogen distillation device and added with a small amount of water washing the bottle.
• the sample flask is attached to a distillation device and a beaker containing 5 ml of 2% boric acid solution is connected to an output of a ball-tipped condenser in the distillation device. Thereafter, 25 ml of a mixed aqueous solution of sodium hydroxide (50% by weight) and sodium thiosulfate (5% by weight) is poured through an inlet for alkali in the distillation device and the inlet and steam port are closed to conduct distillation for 9 minutes.
• the flask is put into an oil bath held at 120° C. and maintained at this temperature for 15 hours. After the completion of the reaction, 100 ml of distilled water is added to the reaction product while cooling to decompose an excessive amount of acetic anhydride and then the acetylated carbon black is taken out through filtration under suction and washed with about 300 ml of the distilled water.
• the acetylated carbon black is placed in a dryer held at 105° C. and dried up to a constant weight, whereby the acetylated carbon black is prepared.
• acetylated carbon black is weighed and charged into a beaker and added with 20 ml of warm distilled water and 2 g of barium hydroxide.
• the beaker is placed in a water bath of 100° C. to conduct hydrolysis for 5 hours.
• the content is cooled in air and filtered under suction with a membrane filter.
• the beaker and the filter are washed with a small amount of the distilled water.
• the filtrate and washed water are combined and passed through an Umberlite IR120 (made by Organo Co., Ltd.) column of a cation exchange resin activated with hydrochloric acid to isolate acetic acid and then the column is washed until the acidity of acetic acid is not observed.
• Umberlite IR120 made by Organo Co., Ltd.
• a calibration curve is previously prepared by using a standard solution of 1/500 normal acetic acid. A quantity of acetic acid is measured from the above titrated value according to the calibration curve.
• a milliequivalent (meq/g) of --OH functional group per 1 g of carbon black is calculated according to the following equation:
• the compounded rubber composition is vulcanized at 145° C. for 30 minutes.
• Tan ⁇ is measured measured by using a dynamic spectrometer made by Rheometrix Corporation at 50° C. under dynamic shearing strain (amplitude: 1.0%, frequency: 15 Hz), and then a reciprocal of the measured value is represented by an index value on the basis that Comparative Example 4 is 100.
• Comparative Example 4 uses 100 parts by weight of tin-modified SBR (S-SBR) as a rubber ingredient.
• the compounding amount of the copolymer as a rubber ingredient is less than 30 parts by weight, the wet-skid resistance is considerably poor

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Tires In General (AREA)

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Cited By (10)

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• 1995
  • 1995-10-27 EP EP95307655A patent/EP0709235B1/de not_active Expired - Lifetime
  • 1995-10-27 DE DE69501999T patent/DE69501999T2/de not_active Expired - Fee Related
• 1997
  • 1997-04-18 US US08/839,348 patent/US5916957A/en not_active Expired - Lifetime

Patent Citations (7)

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